M2-atx hard off when turning ingnition off

Having really hard time installing my carpc. When turning the ingnition on (acc) m2-atx would start the carpc but while starting the car (ingnition on) would shut down hard. When turning off (from on to acc) again hard off instead of graceful shutdown. Works fine on bench or in the car with a simulated ingnition switch (connects to ground or +12v manually). So i figured it has something to do with the ingnition. Do get 0v in off position and +12v in acc/on. Even works if i disconnect the j3 while it's booting when starting the car. The jumpers are in p1 mode but tried other options and get the same behavior. The only thing i could think of is the automatic shut down when voltage drops below 11v, but it would not explain why it does it when turning off or why it does not when j3 is disconnected. Any help would be highly appreciated.

Did another test. Connected power and and ground to an external power supply and j3 to the ignition from the car. Same result, shuts down hard when starting the car or turning it off. The igition reads 0v in "off" position, 12v in "acc"/"on" and disconnected in "start" one

But did you test the voltage on the +12v line with the ignition on and the ignition off?

I don't know what your issue is, but at first glance, it appears that the +12v line is being switched off by the ignition, which would cause the hard off like you describe.
I don't know that this is the case, but measuring that voltage is certainly a good starting point.

Perv is right...everyone should own a decent, inexpensive multimeter...
With that said, are you sure your ACC/IGN into the M2 isn't being shutoff when you crank the motor?
Another user had his ACC in wired to a radio power wire...and of course, the car kills power to the radio when the motor is cranked...

You best bet is to hook the ACC line directly to the ACC line of the car...

Thank you for your replies. I do own a miltimeter and i don't hesitate to use it it's not that i assembled the whole thing and it did not work, i have exausted all possibilities doing all kinds of test for 2 days, i have searched the web, no one seemed to have this issue, which means either i did something wrong, or i have a defective psu, but:
1. It works fine in the car/on the bench if i manually connect j3 to the ground or to +12
2. I did measure all voltages while turning it on/off, cranking and so on. I get around +12 on the "battery" j1 line in the "off" position. It drops down to around +11.4v when i turn it on ("acc"/"on"). Does not drop much while cranking and goes to around +14v with engine running.
3. Since multimeter might not display a short disconnection (you'd need an osciloscope to see in real time what's going on) an to eliminate all doubts i connected it directly to the battery, both j1 and j4, and i mean physically connected 2 temp line to the car battery.
4. Still i thought during cranking the voltage might drop below +11v treshold and could cause the abrupt shot down (eventhough i didn't see on my multimeter). But last night i connected power and ground (j1 and j4) to an external power supply and hooked j3 to the "ig1" from my car (0v in "off", around 11.4v in "on"/"acc", disconnected in "start"/cranking engine and +14v while runnig). It booted up fine when i turn the ignition on and shut down when starting the car. Booted up from the scratch again and did the hard shutdown when turning the ignotion off.
So i am positive it's not wrong wiring and has something to do with "ig1" line in my car, and i can't figure out what it is.

"disconnected in start/cranking"...
No wonder it's shutting off!! It's getting an on signal when on acc, then it's getting an off then on again signal when you crank 'er over!

i'm not sure if acc disconnects during cranking, according to my car diagram it does, but that's not the point. The m2 takes care of it, once booted it goes in autolatch mode and no matter what signal you get on j3 (0, +12v, or disconnected) for the next 60s it would stay on. After that it would use the j3 input to determine whether to do the shutdown or stay on. That's how it is supposed to be and how it is - tested on the bench. While booting up i manually disconnected j3, connected it to the ground wire, repeated several times - as long as it gets power on j1 it would stay on. Anyway that was my next step try to connect j3 to different inputs. Thanks for tour suggestion anyway